A widely and commonly used light fixture in both commercial and residential buildings is the fluorescent light. It has proven to be a satisfactory alternative to incandescent light at least because it consumes less energy and emits less heat. There are still concerns, however, with the amount of energy that a fluorescent light consumes and with the mercury content within the fluorescent tube. With the improvement in light emitting diode (LED) technology, for example in the increase in lumen output at lower power consumption and the ability to be dimmed, the LED lamp is now seen as an attractive alternative to both the incandescent light and fluorescent light. Although ecologic concerns may still exist with LED lamps, these concerns are of less import given the extended lifespan of LED lamps.
A significant challenge to the adoption of LED lighting for use in commercial and residential buildings is the cost to remove and replace a fluorescent lighting fixture with an LED lighting fixture.
United States Patent Application Publication No. 2008/0266849, the disclosure of which is hereby incorporated by reference, suggests that a fluorescent lighting fixture can be retrofitted with one or more LED lamps. The advantage of such a retrofit solution is that the existing fluorescent fixture structure can be retained, thus obviating the need to remove the structure, install a new structure and repair, if needed, any damage to a wall or ceiling caused by the fixture removal and replacement.
Because LED lights operate off of direct current (DC) while fluorescent lights operate from alternating current (AC), the retrofit involves not only changing the lamp itself (from fluorescent to LED) but also changing the electronics which drive the lamp. In one option, this would mean removing the fluorescent ballast circuit from the fixture and installing an LED driver circuit coupled to the AC building mains. Removal of the ballast circuit, however, can be challenging and further involves a significant labor cost. Thus, in another option the fluorescent ballast is retained and an AC/DC power converter circuit is installed at the output of the fluorescent ballast as an interface to the retrofit installed LED lamp.
The reference Nan, et al., “A Driving Technology for Retrofit LED Lamp for Fluorescent Lighting Fixtures With Electronic Ballasts”, IEEE Transactions on Power Electronics, vol. 26, no. 2, February 2011, page 588, the disclosure of which is hereby incorporated by reference, teaches one form of an AC/DC power converter and LED lamp driver circuit for use in a retrofit configuration. A disadvantage of the circuit proposed by Nan is a relatively high cost.
A need exists in the art for a low cost AC/DC power converter and LED lamp driver circuit suited for use in interfacing a fluorescent ballast to power an LED lamp.